This application requests funds to purchase the necessary to provide the Trudeau Institute with a FACS Sorting and analysis flow cytometry capability that will be needed by a group of 13 principal investigators who are studying the basic mechanisms of immune response in vitro and in vivo in models of infectious diseases. The instruments that would be purchased include a (a) FACSCa bench-top flow cytometer with two lasers to allow 4-color, 6 parameter analysis and sorting of small numbers of cells, an Enterprise Coherent Red- diode laser to be coupled to an existing FACSTAR to provide efficient small number cell sorting bases on the dyes best suited to analyzing responding lymphocytes in vivo, (3) a Turbosort for the FACSTAR to allow high speed sorting, (4) a Clone Cyt for the FASTAR to allow deposition of single cells and (5) the computer hardware and software necessary to support the sorting, analysis, data storage and data processing. Together these components will allow us to take advantage of important genetic tools in mammalian biology, including the availability of transgenic mice, which either express one known receptor for antigen or are deficient in particular cytokines or cell surface markers. With these advancements in flow cytometry and instrumentation which require the requested components, one can now transfer well defined populations of lymphocytes or other cells of the immune system, and follow their response in vivo, allowing a new level of analysis of immune mechanisms. The Trudeau Institute is uniquely suited in the study of infectious diseases, but its isolated location makes a stand alone FACS facility and absolute necessity for accomplishing the experimental goals.